a) Field of the Invention
This invention is concerned with a method for producing granulated bean paste (or “miso”), with use of uncooked bean paste as the starting material, which is granulated into small particles, and then dried to have an appropriate hardness to enable it to maintain its form as shaped.
b) Description of Prior Arts
As the prior art for the method of manufacturing such granulated bean paste (or bean paste in granular form), which is prepared from uncooked bean paste, as the starting material, which is formed into granular shape and subjected to desiccation, there is Japanese Patent specification No. 3,151,423.
This method according to the published patent comprises the following steps, that is:
a first step of subjecting the raw material “miso”, prepared by mixing it with seasoning, to a preliminary drying in a vacuum freeze-drying apparatus to render the material to have a low moisture content of an order of 20%, approximately corresponding to the plastic limit of the material to enable it to be extrusion-molded by means of an extrusion-type pelletizer (or granulator);
a second step of breaking and kneading this material bean paste, which has been subjected to preliminary drying to the semi-dried state, by means of an agitator, and then placing the same in a refrigerator for several days to secure homogeneity and uniformity of the water content therein; and
a third step of extruding this semi-dried bean paste (or “miso”), which has been subjected to the homogeneity and uniformity treatment of the water content, is extruded by and through the extrusion-type pelletizer into a space of the vacuum chamber maintained at its degree of vacuum of an order of several hundreds pascals (Pa), in the form of a thin cord of 2 to 4 mm in diameter, while subjecting the extruded material to the vacuum desiccation due to the moisture content decrease on account of abrupt cooling accompanied by the vacuum evaporation of the water content under the vacuum, the shaped product in the cord shape is severed and broken into the granular form by means of a cutting knife disposed within the vacuum chamber, thereby forming the extruded product into the granular form with appropriate hardness to maintain its form as shaped, with further step of subjecting the granular product depending on necessity, to breaking for its second desiccation until it attains a desired moisture content.
This prior art method, however, has its inherent problem such that, when the granular bean paste product is to be made, the resulted granular bean paste contains therein agglomerations in irregular shape which have been generated at a considerable ratio. Removal of such particles of irregular shape contained therein, for the adjustment of the particle size, would inevitably affect the rate of yield of the product, and lower the efficiency in the extrusion-molding.
Occurrence of such irregular-shaped particles to be produced at the time of the pelletization is ascribable to the facts that the water content in this raw material bean paste is lessened to its low moisture content to the order of its plastic limit in the vacuum desiccation at the first step; and that, when the semi-dried bean paste containing therein its water content, which has been rendered homogeneous and uniform at the second step, is shaped in cord-form by the extrusion-pelletizer at the third step, this semi-dried bean paste has, in some of its portions, much more content of water than the water content for its plastic limit. As the consequence, the shaped products in cord-form mutually adhere at the exit part of the extrusion-pelletizer, or become sticked to the exit orifice of the extrusion-pelletizer and coagulated. Such is due to the fact that the water content in this semi-dried bean paste is insufficiently homogeneous and uniform.
On the other hand, the poor efficiency in the extrusion molding is due to the fact that the semi-dried bean paste contains therein a portion, wherein the desiccation has progressed with less moisture content than that for the plastic limit, which causes clogging of the extrusion orifice of the extrusion-pelletizer to result in its obturation. This is also ascribable to the insufficient homogeneity and uniformity in water content of the semi-dried bean paste at the second step.
In order for the semi-dried bean paste to have its uniform water content of upto and including the level of the order of its plastic limit, there is no choice but to refine the entire bean paste material by leaving it in nature so as to have those portions within the material, with the irregular values of its water content matured by storing these semi-dried bean paste material in blocks.
In order to prevent this bean paste material from decomposition which occurs and progresses during its storage, it is indispensable to store this semi-dried bean paste material in a refrigerated condition for a certain period of time. Therefore, the second step of refrigeration in storage in the conventional expedient has its intended merit.
By the way, while it is assumed possible to solve those problems, wherein unconformed particles of the bean paste material would yield during the pelletization, and wherein efficiency in pelletizing becomes poor due to obturation of the extrusion orifice of the extrusion-granulator, can be solved by subjecting the raw bean paste (or “miso”) to a semi-dried state which is slightly lower than the moisture content of an order of approximately its plastic limit, and extruding the raw material by the extrusion-granulator at an increased pressure for the extrusion. In so doing, however, it has been discovered that there derives a separate problem of segregation phenomenon of the oil content in the shaped product as extruded to deteriorate the quality of the resulted product (vide: Japanese Patent specification No. 3,151,423).